1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a method of supporting functionality for roamer port calls in a radio telecommunications network in which Number Portability (NP) is implemented.
2. Description of Related Art
The term Number Portability (NP) is utilized in connection with several types of subscriber service changes in which a subscriber may keep his original telephone number. For example, NP may refer to location portability which involves the capability to physically move (port) a subscriber""s line connection from one switch to another while retaining the subscriber""s original telephone number. NP may also refer to service provider portability which involves changing a subscriber""s service from one service provider to another while retaining the subscriber""s original telephone number. Or NP may refer to service type portability which involves changing the type of service (for example from POTS to ISDN) while retaining the subscriber""s original telephone number. The present invention relates to service provider portability, but is applicable to location portability as well.
FIG. 1 is a simplified block diagram of an existing NP network configuration. All information about ported numbers is loaded from a central database system consisting of several Number Portability Administration Centers (NPACs) 11 distributed throughout the country. In each area, the NP data is downloaded from the NPAC 11 to a Local Service Management System (LSMS) 12 in order to populate network elements 13-15 deployed in the NP network with the ported subscriber data. The network elements 13-15 may comprise service control points (SCPs) and/or service transfer points (STPs). Each service provider may implement its own LSMS, and each LSMS is notified by the NPAC which numbers are ported. In this way, callers in different networks continue to dial the subscriber""s original number, and each network is aware of the fact that the dialed number has been ported, and routes the call accordingly.
Each portable number is identified by its Numbering Plan Area Office Code (NPA-NXX), where the NPA relates to the area code, and the NXX relates to the exchange code. For example, in the telephone number 214-997-1234, the NPA is 214 and the NXX is 997.
The ported subscriber data downloaded from the NPAC 11 and LSMS 12 for a single subscriber is grouped into a single record called an NP subscription. The information contained within the NP subscription is the routing data necessary to route a call to the subscriber""s new location or new service provider""s switch. The information is categorized as Location Routing Number (LRN) data and Global Title Translation (GTT) data. GTT data is necessary for the routing of services such as Line Information Database service (LIDB), Custom Local Area Signaling Services (CLASS), Caller ID With Name (CNAM), and Interswitch Voice Messaging (ISVM). Upon reception of this information from the NPAC 11, the LSMS 12 populates the LRN and GTT functions deployed in the network elements 13-15 with the relevant data elements.
NP has been implemented in wireline telecommunications networks, and FIG. 2 is an illustrative drawing illustrating the steps involved when retrieving a Location Routing Number (LRN) in an existing wireline telecommunications network having NP service provisioning. At 21, a calling subscriber dials the telephone number of a called subscriber 26, for example 214-997-1234. The call is routed to an originating switch 22. There are mechanisms set up within the originating switch to recognize that the NPA-NXX (214-997) has been made open for portability. Therefore, a lookup is performed in the NP database 23 of a SCP associated with the originating switch to retrieve a LRN corresponding to the dialed telephone number. If the NP database indicates that the dialed number is not ported, then the dialed number (or an empty response) is returned to the originating switch. If the dialed number has been ported, the LRN of a recipient destination switch 25 is returned. The originating switch then routes the call on the LRN at 24 to the destination switch 25 which handles the NXX in the retrieved number (e.g., 881). The dialed telephone number is also carried in signaling, for example in the Generic Address Parameter (GAP) of ISUP common channel signaling. The destination switch replaces the LRN with the dialed telephone number since the called subscriber 26 is still using the dialed telephone number. The call completely bypasses the 997 NXX switch 27.
The Federal Communications Commission (FCC) has directed that NP be implemented in wireless radio telecommunications networks as well. Additional complexities are encountered in wireless networks due to the mobility of the subscribers. In wireless ANSI-41 networks today, a subscriber""s Mobile Directory Number (MDN) and his mobile station""s Mobile Identification Number (MIN) are generally identical. Several wireless features are built on the assumption of MIN-MDN equivalence. After the introduction of NP in wireless networks, a subscriber can keep his directory number as he changes from one service provider to another. However, when porting to an ANSI-41 network, the subscriber"" mobile station is assigned a MIN that is generally different from his MDN. MINs are not portable in ANSI-41 networks, and each MIN series is tied to a particular home location register (HLR). Hence, features that assume MIN-MDN equivalence are impacted.
In particular, the implementation of NP impacts features such as functionality for roamer port calls delivered locally or after a location query to an HLR. Many operators support at least one roamer port in their networks. Roamer port numbers utilize two-stage dialing procedures to enable subscribers operating in the same local network to call each other without incurring long distance charges even though they are from different home networks. For example, if a subscriber from Montreal travels to Dallas and registers there, a calling party in Dallas can utilize the roamer port in Dallas to call the Montreal subscriber without incurring long distance charges. The calling party may be a mobile subscriber or someone calling from the PSTN. The roamer port belongs to the MSC of the Dallas service provider, with whom the Montreal subscriber""s service provider has an agreement. The Dallas calling party dials the roamer port number for the roamer port mobile switching center (MSC) which is a local number. He then gets a second dial tone, and xe2x80x9cover-dialsxe2x80x9d the Montreal subscriber""s MDN. The roamer port number is defined in the Dallas MSC in which the Montreal subscriber is operating, and may serve the entire service area of the Dallas MSC or some sub-area thereof The roamer port number tells the Dallas MSC to page for the roaming mobile subscriber in the roamer port service area. In this manner, the Dallas calling party is able to call the Montreal subscriber who is roaming in the Dallas network without using long distance trunks or incurring long distance charges.
Paging in wireless networks is performed utilizing the MIN of the mobile station rather than the subscriber""s dialed MDN. Before the implementation of NP, the MDN and MIN were equivalent, so the MSC owning the roamer port could page the called mobile station using the dialed MDN. With NP, however, the MDN and MIN become distinct and separate numbers if a number is ported, and the MSC that has the roamer port must translate the over-dialed MDN to a MIN in order to page the subscriber and deliver the call.
Additional complexity is added by the fact that in metropolitan areas, a single roamer port can be shared by several MSCs. In this case, the current functionality is such that the MSC having the roamer port first checks in its own records to see if the MIN (equivalent to the dialed MDN) is being served. If so, the called mobile station is paged with the MIN, and the call is connected. If the MIN is not being served, the MSC sends a Location Request (LOCREQ) message to the called subscriber""s HLR to find the subscriber""s location. If the called subscriber is in one of the neighbor MSCs that is sharing the roamer port, a trunk is set up and the call is completed; if the called subscriber is not in the local area, the call is not completed.
To route the LOCREQ message to the proper HLR, the MSC consults its internal data structures to determine, based on the dialed MDN, which HLR to query. These internal data structures are manually-maintained lists of MDN-MIN or MDN-HLR associations. This method is feasible today because, in general, the MDN and MIN are identical. After the implementation of NP, however, maintaining these tables becomes unrealistic, since every MSC would have to update a MIN-MDN association for every subscriber every time a subscriber ports somewhere in the network.
There are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein. It would be advantageous to have a method of supporting functionality for roamer port calls in a radio telecommunications network in which Number Portability (NP) is implemented. The present invention provides such a method.
In one aspect, the present invention is a method of supporting functionality for roamer port calls delivered locally or after a location query to a Home Location Register (HLR) in a radio telecommunications network in which Number Portability (NP) is implemented. The network includes a plurality of mobile switching centers (MSCs). The method includes the steps of storing in each MSC, based on information received in the registration process, an association between a mobile identification number (MIN) and a mobile directory number (MDN) for each served mobile station (a MIN-MDN pair). When a roamer port call, which includes the MDN of the called mobile station, is received in a roamer port MSC, the roamer port MSC identifies the MIN of the called mobile station. Using the MIN, the roamer port MSC may page the mobile station in an attempt to deliver the call, or may instead utilize the MIN to identify the home location register (HLR) of the called mobile station. The method may then utilize the identified MIN to route a location request message to the identified HLR for call delivery or to invoke any active call-diversion type services.
In another aspect, the present invention is a method of supporting functionality for roamer port calls delivered locally or after a location query to a HLR in a radio telecommunications network in which Number Portability (NP) is implemented. The network includes a roamer port MSC having a roamer port which is shared with at least one neighboring MSC. Each MSC stores a MIN-MDN pair for each served mobile station. When a roamer port call, which includes the MDN of the called mobile station, is received in the roamer port MSC, the roamer port MSC determines whether it has stored a MIN-MDN pair for the called mobile station. If not, the roamer port MSC sends a message to the neighboring MSC inquiring whether the neighboring MSC has stored a MIN-MDN pair for the called mobile station. If so, the neighboring MSC may send the MIN, an indication of a trunk resource, or both to the roamer port MSC. If only a MIN is sent, the roamer port MSC then identifies the HLR of the called mobile station utilizing the identified MIN and issues a location query to the identified HLR to progress the call. If only an indication of a trunk resource is sent, the roamer port MSC may trunk the call to the neighboring MSC which then may either page the called mobile station directly or issue a location query to the HLR. If both a MIN and a trunk resource indication are sent, then internal procedures in the roamer port MSC determine which action to take.
In yet another aspect, the present invention is a method of supporting functionality for roamer port calls delivered locally or after a location query to a HLR in a radio telecommunications network in which NP is implemented. The network includes a roamer port MSC having a roamer port which is shared with at least one neighboring MSC. Within a number portability database (NPDB), a location routing number (LRN) is associated with each distinct MSC/HLR pair in the network. When a roamer port call, which includes the MDN of the called mobile station, is received in the roamer port MSC, the roamer port MSC determines whether the MDN for the called mobile station falls within a portable range. If so, a request is sent from the roamer port MSC to the NPDB to retrieve a LRN for the called mobile station, the request including the MDN for the called mobile station. From the LRN, a HLR associated with the mobile station is identified. The roamer port MSC then sends a location request to the identified HLR using the LRN as a global title address or using a LRN-HLR association table to route the location query. The HLR returns a routing number for the called mobile station. This is followed by determining whether the called mobile station is located in a location to which call delivery is allowed by the roamer port MSC.
In another aspect, the NPDB is modified to associate with the dialed MDN, a HLR pointer for the HLR where a subscriber record is maintained for the called mobile station. When a roamer port call is received in the roamer port MSC, and the MDN for the called mobile station falls within a portable range, the roamer port MSC retrieves the HLR pointer from the NPDB. This is followed by sending a location request from the roamer port MSC to the identified HLR, sending a routing number for the called mobile station from the HLR to the roamer port MSC, determining whether the called mobile station is located in a location to which call delivery is allowed by the roamer port MSC, and routing the call upon determining that the called mobile station is located in a location to which call delivery is allowed by the roamer port MSC. Alternatively, the NPDB may be modified to directly associate a MIN with the dialed MDN, and the MIN may be returned to the roamer port MSC from the NPDB so that the MSC can use the MIN to determine which HLR to query for location information.